Steam-engine valve-gear



C. F. PRESCOTT.

STEAM ENGINE VALVE GEAR.

APPLICATION FILED MAR 13. I919.

1,340,405. Patented May 18,1920.

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WITNESSES INVENTOR W f v C. F. PRESCOTT.

STEAM ENGINE VALVE GEAR.

APPLICATION FILED MARE13, I9l9.

- Patented May 18, 1920.

wwwfi s Q Q WITNESSES W UNITED STATES PATENT OFFICE.

CHARLES F. IRESCOTT, 0F BROOKLYN, NEW YORK.

STEAlNI-ENGINE VALVE-GEAR.

Application filed March 13, 1919.

To all whom it may cmwern:

Be it known that I, CHARLES F. PRESCOTT, of Brooklyn, in the county of Kings and State of New York, have invented a certain new and useful Improvement in Steam- Engine Valve- Gears, of which improvement the following is a specification.

My invention relates to locomotive engine valve gears of the radial type, more particularly those known as Walschaerts gears, and its object is, primarily, to attain the advantage of reduction of cost of con- .struction and 'maintenance by providing a radial mechanism which shall be operative for the performance of the function of the slotted link applied in prior constructions. A further object of the invention is to effect a reduction in the weight of the moving parts of the valve operating mechanism, and thereby to reduce the objectionable strains resultant upon inertia.

The improvement claimed is hereinafter fully set forth.

In the accompanying drawings: Figure 1 is a side View, in elevation, of a valve gear illustrating an embodiment of my invention, as applied on a locomotive engine; Figs. 2 and 3, similar views, on an enlarged scale, showing the gear in position for forward, and for backward motion, respectively; and, Fig. d, a plan or top view.

As will appear by reference to Fig. 1 of the drawings, the general operative principle of my invention accords substantially with that of the well known \Valschaerts gear, actuation being, in bothcases, effected by connections with a return crank on a locomotive driving wheel and with a cross head, respectively.

In the practice of my invention, referring descriptively to the specific embodiment thereof which is herein exemplified, and to the gear on one side only of a locomotive, which is similar to that on the opposite side, I provide a vibratory link carrying frame, 1, comprising two plateswhich are disposed in parallel vertical planes, and are each in the form of a bell crank lever, having a short upper arm and a long lower arm, at substantially a right angle thereto. Laterally projecting trunnions, 2, are formed, in line axially, on, or are secured to, the plates of the frame, 1, at the junction of the short and long arms thereof,

Specification of Letters Patent.

Patented May 18, 1920.

Serial No. 282,382.

and are journaled in hearings on a suitable support, 3, fixed to the frame of the locomotive. The lower long arms of the frame,

1, are coupled, by a pin, 1 to one end of an eccentric rod, 9, the opposite end of which is coupled to an eccentric crank or return crank, 10, fixed on one of the driving wheels, 11, of the locomotive.

The end of the radius bar, 5, farthest from the steam distribution valve, 15, is coupled, by a pin, 5, to a pair of parallel floating links, 5", which are, in turn, coupled, by a pin connection, to the upper end of a guide link, 1, the lower end of which is coupled, by a pin, 1, to the long arms of the frame, 1, at points thereon exterior to their longitudinal central planes, and on the side of said planes farthest from the short lever arms. links, 5", are coupled, intermediate of their end connections, to the short lever arms of the frame, 1, by radial links, 1

The radius bar, 5, is coupled, adjacent to its rear end, bya lifting link, 6, to a lifting arm, 6", on a reverse shaft, 6, which is journaled in bearings in suitable supports, 7 carried by the locomotive frame, and the radius bar is raised and lowered, to effect adjustment for forward or back motion, or variation of the point of cut off, by appropriate movements of the reverse shaft about its axial line. Such movements are imparted to the reverse shaft, as from time totime desired, through a reach rod, 8, coupled, .at one end, to an upwardly extending arm, 6 on the reverse shaft, and at the other, to a manually operable reverse lever (not shown) or to a power reversing mechanism of any suitable and preferred construction. The forward end of the radius bar, is, as in prior c0nstructions,'c0upled to a combination lever, 12, connected, by a union link, 12, to the cross head, 13, in the manner of the ordinary VValschaerts gear, the combination lever being connected to the stem, 14:, of the distribution valve, 15, by which steam is admitted to, and exhausted from, the engine cylinder, 16.

In operation, the raising or lowering of the radius bar, 5, within different degrees of traverse, by rocking movement of the reverse shaft, 6, in its bearings, as caused by proper movement of the reach rod, 8, and its operating connections, will effect .the neces- The floating sary adjustment of the valve gear for forward or back motion, as the case may be,.and for the desired point of cut off. The rear end of the radius bar will, in such adjustment, move through a comparatively flat arc, which is concentric with the axis of the pin by which the radius bar is coupled to. the combination lever, and, in such movement,

a will be controlled and guided by the floating links, 5*; the radial links, 1*, by which the floating links are coupled to one arm of the link carrying frame, 1; and the guide link, 1, by which they are coupled to the other arm of said frame. As the end of the guide link, 1, which is connected to the radius bar, moves in an are about the axis of the pin, 1, at its lower end, the arc traversed by the adjoining end of the radius bar, varies, toward its ends, slightly from a geometrically true one, but the inaccuracy is presented outside of the ordinary working range of the mechanism, and is of such slight magnitude as not to be appreciable in operation.

The movements imparted to the link carrying frame, 1, from the eccentric rod, 9, are imparted to the radius bar through the radial linkage described, instead of being transmitted through a slotted link, and these movements in combination with the movements of the cross head, transmitted through the combination lever, 12, reciprocate the distribution valve, in the same manner as by the mechanism of the ordlnary Walschaerts valve gear.

The radius bar being, as shown, connected positively to the eccentric crank operating mechanism, instead of through the intermediation of a block sliding in a segmental link, as in the ordinary constructimi, it re suits that, as the slip of a block in a link is thereby avoided, positive movement is imparted to the radius bar and connected dis tribution valve, in any and all positions to which the radius bar may be moved for adjustment of the point of cut off, in either forward or back motion. Further, as only pin or pivotal connections of the operating members are required, they may be fitted with an economy of machine shop work, and maintained in operation at minimum cost.

I claim as my invention and desire to secure by Letters Patent:

1. The combination, in a steam engine valve gear, of an eccentric crank; a radius bar; a valve stem connected to the radius bar; a vibratory link carrying frame, journaled, at one end, in fixed bearings, and having long arms positively connected to the eccentric crank, and short arms, at an angle to its long arms; a radial linkage positively connecting the radius bar to the long and to the short arms of the link carrying frame; and a vibratory reverse shaft, having an arm coupled to the radius bar.

2. The combination, in a steam engine valve gear, of an eccentric crank; a radius bar; a valve stem connected to the radius bar; a vibratory link carrying frame, journaled at one end, in fixed bearings; and having long arms positively connected to the eccentric crank, and short arms at an angle to its long arms; floating links coupled, at one end, to the radius bar; guide links connecting the opposite ends of the floating links to the long arms of the link carrying frame; radial links coupling the floating links, intermediate of their ends, to the short arms of said frame; and a vibratory reverse shaft, having an arm coupled to the radius bar.

8. The combination, in a steam engine valve gear, of an eccentric crank; a radius bar; a valve stem; connected to the radius bar; a vibratory link carrying frame, of bell crank form, positively connected to the eccentric crank; a radial link pivotally con- .nected to the short arm of, the link carrying frame; and a floating radial link, through which motion is imparted from the eccentric crank to the radius bar, said floating link being articulated, at one end, to the radius bar, and coupled, at the other end, to the link carrying frame, and articulated, between its ends, to the first specified radial link, so as to move the radius bar in an arc of a circle.

CHARLES F. PRESCOTT. \Vitnesses:

J. SNOWDEN BELL, A. S. VANDERBILT. 

